The Modern Iranian languages are those languages that gradually emerged in the different parts of Iran after its conquest at the hands of the Muslims and even though some of them existed simultaneously with some of the Middle Iranian languages, major developments can be found in their structures that make them distinct from the Middle Iranian languages. Some historians and geographers of the Islamic Era like Estakhri (in his books, “Al-Masālek” and “Al-Mamālek”), Moqaddasi (in “Ahsan al-Taqāsim”), and Hamdollāh Mostofi (in “Nahzah al-Qolub”) have mentioned the names and occasionally even some examples of the words or sentences of some of the Modern Iranian languages and dialects that were in use in the different parts of Iran prior to the 10th Century AH/16th Century AD.

Today, the main centers of the Modern Iranian languages comprise Iran, Afghanistan, and Tajikistan. However, some of these languages are also in use in the Central Asian Republics, the Chinese Turkistan, Turkey, the Persian Gulf countries, Syria, the Indian subcontinent, Iraq, the Pamir Plateau, and the Caucuses. From among the Modern Iranian languages only Fārsi (with its three main types, viz. Iranian, Afghan, and Tajik) as well as Yaghnābi have survived directly from the Middle Persian and Soghdian languages whereas the origins of the other Modern Iranian languages are ambiguous.

The most important and the most widely spoken Modern Iranian language is the “Dari Fārsi” which shall be dealt with in detail later. The other Modern Iranian languages and dialects that run into hundreds in number have been categorized in the two main Western and Eastern groups on the basis of their structural and geographical affinities.